The word telemetry did not come into use until some medium of transmission had been invented. Since it is defined as the communication of measurements that were taken from some distant point, the earliest telemetry system was one based on a electrical wire. Following the invention of the telegraph and later the telephone, one of the earliest known United States patents for a telemetry system was granted in 1885. These first telemetry systems were used by electric power companies to monitor the distribution and use of electricity throughout their systems. They were called supervisory systems because of their monitoring abilities. One of these original telemetry systems was installed in Chicago, Illinois, in 1912. This network used the city's telephone lines to transmit data on its several electric power generating plants to a central control station. Following World War I, this data was transmitted by the electric power lines themselves. Although electrical telemetry systems are still in use, most modern telemetry systems use radio transmissions to span substantial distances.